FIG. 1 is an illustration showing a general data transmission/reception system. When referring to FIG. 1, the general data transmission/reception system can comprise a data transmission terminal SENDER and a data reception terminal RECEIVER.
The data transmission terminal generally transmits data by modulating a digital signal using frequencies. Here, a signal modulation technique can include an amplitude shift keying (ASK), a phase shift keying (PSK), and a frequency shift keying (FSK).
Recently, a technique which transmits (or sends) data through an audible frequency for humans (an audible frequency band) has been introduced. The audible frequency band of human is a range of 20 Hz-20 KHz, and for voices, ranges of 85-180 Hz and 165-255 Hz bands are mainly used for men and women, respectively. As for currently available terminals, they have speakers and microphones which are designed to support all the audible frequency band in order to transmit and receive human voices.
When data transmission/reception is performed by using an audible frequency which is not easily recognized by humans, it is beneficial because the data transmission/reception using terminals can be realized without requiring a separate hardware device. Also, when an audible high frequency is used, no pairing process is required between devices, which results in an easy data delivery. However, according to the conventional data transmission method using an audible high frequency, a transmitted data is represented by combining predetermined frequencies, and it does not perform any process on noises or interferences which are collected in the data transmission environment, which causes a recognition rate to fall since it is hard to discriminate a signal from the noise when an interference exists in the preset frequency band.
Meanwhile, the description set forth as the background of the invention in the above is merely provided to ease the understanding on the background of the invention, and it can no way be regarded as an admission as the prior art which is already known to a person with ordinary skill in the art.